Summary: ORIGINAL ARTICLE
Leticia AvileÂ s á Cora Varas á Eric Dyreson
Does the African social spider Stegodyphus dumicola
control the sex of individual offspring?
Received: 21 October 1998 / Received in revised form: 23 March 1999 / Accepted: 26 April 1999
Abstract By scoring the chromosome number of de-
veloping embryos, we show that the sex ratio bias of the
African social spider Stegodyphus dumicola Pocock is the
result of an overproduction of female embryos. Only
17% of 585 embryos sexed from 14 egg sacs were male, a
signi®cant departure from a 1:1 sex ratio. We also
explored the possibility of direct control of the sex of
individual ospring in this species by examining the
variance in the number of males per sac and the spatial
distribution of male and female embryos within the sacs.
We postulated that a variance in the number of males
per sac lower than binomial (i.e., underdispersed or
precise sex ratios) or a non-random distribution of male
embryos within the sacs would suggest direct control of
the sex of individual ospring. We found that the vari-